The present invention relates to the field of display systems, with particular emphasis on the area of computer generated imagery for training purposes.
Generating an image electronically is not a new idea. It was developed some years ago. Relatively recent efforts have expanded the technique significantly as electronic gadgetry became popular to foment a state of art that is now widely conventional at the lower spectrum of sophistication. And, the demand continues to expand, to extort greater capability from available capacity.
Until recently, a computer image generator (CIG) was used rather tentatively in training devices. The need for more image information was recognized but the cost of improving the scene was a burden that exceeded the allotted equipment. Accordingly, numerous approaches have been utilized to render the scene viewed by the trainee more realistic with the equipment on hand. In other words, the objective is efficiency. And it is to that end, that the present invention is oriented.
Ideally, the view observable by a trainee occupying a training device is a perfect reproduction, a total simulation, of a scene realistic to operational conditions. Achievement of that goal may be attainable, but at a very high cost of equipment capacity. Computers are expensive and the amount of computing capacity and bandwidth that would be necessary to faithfully produce a realistic scene over a full field of view would be enormous. The alternatives are to take the approaches of the prior art.
Small scale presentations of virtual images presented close-in to the trainee's eyes have found application in the field. The display is most often projected onto an attachment to a helmet worn by the trainee. Helmets are specially designed for the purpose by incorporating a cathode ray tube, or the like, within the structure, such as is shown by the U.S. Pat. Nos. to Stanton, 3,059,519 and to Bradley 3,205,503. In all such arrangements, the instantaneous field of view is limited and the scene observed by the trainee somehow lacks realism.
Other techniques utilized or attempted include projecting images onto a wind screen, or the like, that is spaced before the trainee. The images may be projected from behind or near the trainee, or from beyond the wind screen as shown in U.S. Pat. No. 3,949,490 to Derderian. The technique is reasonably effective for some applications such as the presentation of flight information, but is less desirable for dimensional scenes than a wide angle viewing screen more remotely spaced from the observer. The best technique for overall realism employs a dome; a dome that encloses the trainee, his simulated vehicle environment if he has one, and the visual arena for the training encounter.
The domed training device presents the scenes that are preplanned for the training session onto the surface of the dome. The dome is spaced apart from the trainee and is most often spherical. It is either reflective or translucent, so that the images are presented from either inside the dome onto its inner surface or from outside by rear projection techniques. Most that have found any utilization have been of the reflective type.
The most elementary of the domed devices simply projects a wide angle view of a movie onto the inner surface of the dome. The next step involves presenting a television projection of a modelboard onto the reflective screen inner surface of the dome. The modelboard is a miniaturized layout not unlike an elaborate toy train setting which has been faithfully reproduced to scale. A gantry mounted television camera can be made to move over the board and view it from various angles to create a scene inside the dome reminiscent of flying. To find acceptance by users the technique has been expanded to link the movements of the camera to the trainee's responses. By that, it has become useful to train vehicle operators. And, the systems have been expanded on by placing the dome on a motion platform. Not only the visual feel of the scene is provided thereby, but also the complementing feel of motion. Realism is heightened.
An approach that has been recently developed as an alternative or addition to the television system is in computer generated imagery (CIG). Images are programmed, and a sequence is projected that is responsive to the operator's controls. The computer is programmed to provide electrical signals that appear as physical objects when displayed. Extensive programming is required, and programming techniques have been originated to place the requirements within the state of the existing art. The size of the undertaking is not fully understood until it is realized that the computer generated image must change not necessarily in a predetermined fashion, but in response to the relatively unpredictable actions of the trainee. But, these requirements have been met, and operational systems are in existence and being used in the pilot training field by commercial firms and the Government.
CIG may occupy a small portion of the display and be supplemented by a separate background, or the computer may be overextended to provide a display over the full field of view. In the latter, the scene lacks definition and realism is discarded. For the system to be useful, more computating equipment and bandwidth have always been the solution. In the former, a contrast of styles and the need for accurate blanking of the television background coincident with the overlayed computer generated image, have been disadvantages. Multiple CIG scenes have been turned to as a solution. A wide angle field of view can be composed of several narrow fields of view separated by blind spots, or in dual channel systems only the primary image, such as an aircraft carrier, is presented with a degree of sophistication. The background is presented with less resolution, requiring less equipment to process it. Problems still stand in the way, however, when the terrain to be presented is complicated.
People have peripheral vision. Not only is the primary area observed noted, but the remainder of the field of view plays a large part in our total sense of space. Most of our attention is directed toward what we look at, but we see adjacent objects well and can recognize others at some distance removed. And, even on the very perimeter of our vision we can detect motion.
The prior art has approached the display question by proposing a full field of uniform resolution, or by proposing a uniform background supporting a spot of higher resolution. Neither has been found to be totally satisfactory, and each has been determined to be unsatisfactory where the responses of an aircraft pilot are to be improved in an arena where terrain is a factor.
The patent to Dr. A. M. Spooner (U.S. Pat. No. 4,048,653) exemplifies the state of the art in the field of the present invention. There, a helmet mounted arrangement for projecting an image into a pilot's line-of-sight is disclosed. The image is presented onto the viewing screen as two images spaced slightly apart, with the right image polarized to be visible by only the right eye of the pilot and the left image similarly polarized for the left eye. The scene viewed may be from any source, although the majority of the disclosure is devoted to describing the optical link between a modelboard and the projection screen. The link includes an optical probe that is slaved to the pilot's head. As the probe is moved forward over the board to simulate flight, the portion to the left is viewed by the probe if the pilot looks left; and the portion to the right is viewed when the pilot looks right.
The patent does not ascend into the confines of computer generated imagery. That arena presents problems that are not addressed by the patent. While it may be possible to generate a high resolution image in motion over a full field of view, it is not practical. Too much computing space and bandwidth would be required. And, the alternatives provide pale imitations of realism, as discussed above.
As system needs have increased, the computers capability has increased, but not at a comparable rate. The number of edges a system can process has gone from 500 in 1972, to 8000 edges for systems that will be operational in 1980. And, although the cost-per-edge has decreased during that period, the total cost has climbed.
Until recently it was felt that still greater capacity for edge processing was required to overcome the cartoonish nature of the images. But, several new techniques by others are beginning to show promise. For example, it has been demonstrated that most of the texture of a scene can be supplied by means other than defining specific edges. Evidence is showing that by far the most efficient approach to producing a given scene is by defining only the main features by edges and then adding a variety of textures to increase realism.
The optimistic developments that have been described only provide us an opportunity to create improvements in time to meet the crushing demand for expansion of the data bases for CIG displays. Recently, normal requirements have not exceeded 100,000 edges, but new requirements soar to over ten million units. Fortunately, other developments are tending to accommodate what would otherwise be a superior task of generating such a data base. First, there is now some understanding of how to use point lights to define features. Second, automated techniques for the generation of data bases are becoming available. And third, object generators with dedicated chips could be developed that contain the features of an item, vehicle, or other object of interest which can be manipulated without placing demands on the data base. The need will nevertheless exist for an efficient computer generated image display, a need that is addressed by the present invention.
An objective and advantage of the present invention is to provide a display of computer generated images that allocates edges or other forms of resolution by proximity to the observer's instantaneous area of interest. Accordingly, available resources of equipment and bandwidth are employed with efficiency to provide a dynamic display that corresponds to the visual acuity of the observer.
The present invention includes a computer generated image that is projected onto a distant screen by apparatus which aligns with a trainee's line of sight, as determined by an eye tracker, and head tracker where desired. The image generator is programmed with a preselected scene arrangement and is responsive to operator actuated controls to simulate a flight, for example. The generator is also responsive to head, and most preferably, eye movements of the operator to apportion definition of the image within the scene displayed.